Abstract: The Environmental Protection Agency (EPA) compiles data on emission tonnages of air pollutants for US counties.  US Air Quality Gradebook ("AirGrades") source sheets such as this one for Midland County, Texas, and

Milam County, Texas, give the percentage contributions from specific air pollution sources.  The Midland County Seat is Midland, Texas, and the Milam County Seat is Cameron, Texas.